i have done windows 10 OS in my hp laptop by the way i lost all my data in hard disk. Any one tell me hoe to recover my data back?
Usually if you choose "Upgrade", Windows 10 preserves access to your data. If you did a "Custom Install", it does not. It sounds like you did a Custom. All is not lost. Your data is still mostly on your hard drive, but Windows can't find it. Certain recovery programs can. I list them later. Stop writing to the hard disk, because every time you do, maybe you overwrite your old data and it will be lost. Do a fix now.
If it's not more than 30 days since the upgrade to Windows 10, you may be able to go back to your earlier OS. Your old OS is in a directory called Windows.old and can be restored in certain cases. Then you should copy your data to USB and save it to add back when you reinstall Windows 10. This is a good reminder to back up your data often, if you don't want to lose it.
If you can't go back to your earlier OS, then you can try recovery. There are zillions of programs which claim they do this, with varying success. Some are free programs, others cost money. You can look at these highly recommended free ones --- and good luck recovering your data: